GUN So, I got a scope mount for my Mosin...

The kit came with the mount, a bolt handle, 3 screws, a spacer, 2 drill bits, and a tap

Guess I'm going to have to do some gunsmithing

Anyone ever do this? I may fuck it up

And, before anyone asks, I have access to a metal shop and have some background in metal fab, so it shouldn't be too hard. I'm not too sure about using a hacksaw to lop off the stock bolt handle though

You can get a bolt with a turn-down handle, no need for hacking it off. The pin on the rear sight could be soldered in. In that case, obviously, you need to de-solder it. Otherwise, you either punch/press or drill the pin out, I've heard of people doing both. With your metal fab background I'm sure you could figure out the best way to do that. Plenty of reading material online if you google for it; I don't have the links handy.

Btw, I haven't done it myself yet, just talked to and read of several who have.

I went thru this a few years ago. The mount which comes with a bolt handle is made by ATI.
The scope mount screws down atop the receiver using holes that you drill and tap into the receiver. The mount extends back into the area where the bolt handle travels when you operate it. There's little clearance and you must cut off the old handle and install the new one which is quite flat at the end that fastens to the bolt.
I did this to my M44 and the bolt handle, which is held on by one screw, is a potential weak point.
I finally, in the name of reliability, bought a bent-handle bolt only to find that, even with a sharp bend, it won't clear.
The solution was to send the bolt to the Boltman who welded a really great handle onto my bolt. His handle is flat where he welds it on and it looks like it came that way. He's got pictures of his work on his website.
It finally came out nice but, if I were to do it over again, I'd do it different. They make a scope mount that replaces the rear sight. The whole thing stays forward enough that it never gets in the way. You can find them on Ebay, and elsewhere. Only thing is...you then need a long eye-relief scope. That's what all pistol scopes are. The optics are set up for your eye being 10-18" back.
If you DO use the ATI setup, cut off the handle, leaving the stub too long. Then cut it down on a milling machine so it's square and accurate. Also, make sure that you leave no burrs inside the firing chamber when you drill and tap or you'll have trouble ejecting.